Your recordings are probably very quiet if you need to tenfold the volume. When you convert to MP3 you probably don't increase the volume BEFORE the conversion, so encoder's psychoacoustic model discards a lot of sound being nearly under the threshold of hearing - hence the quality loss. MP3 conversion is a useless step in your case anyway.Try the following:

1. Increase the volume of WAV with ReplayGain (look it up too) to a de-facto standard level2. Process the WAV with LossyWAV so it is more compressible3. Convert to (lossy)FLAC

It would be desirable to record closer to the sound source or with a more sensitive device so you can skip the 1st step and get better bit-depth/SNR (currently your sound is probably under 13bit/78dB SNR).

At the 2:34> mark I can hear ticks, pops and noise, including what sounds like talking or maybe a tv going in background? WTH? This is listening with in living room with custom active 8" 2 way monitors. I'm sure the headphone guys will chime in with more detail.Lastly, I realize its a Zoom recording in room, but the SQ is abysmal (per my >audiophile standards). Hopefully/should be much better on site

I listened to the ZOOM... FLAC, and it was so bad that had to listen to something else to reassure myself that something wasn't broken. I can confirm the tics you mention. Vinyl does not have to sound this bad, and vinyl from the 60s doesn't have to sound this bad.

File size - For uncompressed files, file size is simply the product of sample rate (kHz), bit depth (converted to bytes), number of channels, and the playing time. As long as you know there at 8-bits in a byte, it's a straightforward calculation. For example, CD audio is 44.1kHz, 16-bits, 2-channel stereo. That's 44,100 samples per second x 2 bytes x 2 channels = 176,400 bytes per second, which works-out to about 10MB per minute. A mono file will be half the size of a stereo file. A 24-bit file is 50% bigger than a 16-bit file. (An 8-Bit file would be half the size but probably unacceptable quality.)

A FLAC will be about 60% the size of the uncompressed original. (You won't get as much compression with mono, but the mono starts-out smaller.)

Quote

I increase the volume to 999% (software limit)

I don't know what that means. Most audio editors/tools (Audacity/GoldWave/Sox, etc.) have a normalize (maximize) function that adjusts the volume as high as possible without clipping (distortion). That's often not loud enough because one "loud peak" limits the volume of the entire program. To get-around that, you can use limiting or dynamic compression to "push down" the peaks and then boost the overall volume. and continue with the conversion, doing math to calculate the highest bitrate possible that will still get me under or at 291 MB.

Quote

doing math to calculate the highest bitrate possible that will still get me under or at 291 MB

I'm not sure what you mean by that... With FLAC you have very-little control over the bitrate, except that you can start with a lower-bitrate original (a lower sample, rate or lower bit-depth, etc.).